Three-phase Motors Three-phase induction motors brushless motors.

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Three-phase Motors Three-phase induction motors brushless motors.

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Three Phase Motor Control with ST52
Three-phase Motors
Three-phase induction motors brushless motors. stator copper wound rotor typically made aluminum squirrel cage. motor supplied with three sinusoidal voltage waveforms which produce rotating stator field. speed adjusted field frequency. rotor follows this field with called slip. slip
Induction motors with squirred-cage workhorse industry because their cost rotors rugged construction. When operated directly from line voltages, induction motor operates constant speed. means power electronic converters, possible change speed motor. side benefit, induction motor drives results energy conservation.
STFive Applications
Three-Phase Induction Motor Scalar Control Mode
Scalar control typically achieved controlling voltage frequency rati control) open closed loop. Optimized motor efficiency achieved implementing slip control.
ST52
STFive Applications
Speed control varying stator frequency voltage (V/F)
speed controlled varying (frequency stator voltage), which controls synchronous speed (and, hence, motor speed, slip kept small), keeping flux constant varying linear proportion Varying stator frequency voltage preferred technique most variable-speed induction motor drive applications.
STFive Applications
Torque versus Rotor Speed constant
Torque/T, rated
Pull-out Torque Flux decreases
Maximum torque
Stable zone
rated
Unstable zone Motor stops
rotation speed
rated
Flux =rated
rotor speed
1.0f
0.8f
0.6f
0.4f
0.2f
slip
f-fr)
frequency
slip
STFive Applications
Torque-Speed Characteristics
small value slip (Fsl=Fs-Fr) keeping flux constant result linear relationship between Torque Fsl(slip) value shown.
Constant Load
Fsl4
Fsl3
Fsl2
Fsl1
Fsl0
Rotor speed increasing Stator Frequency increases Speed controlled varyihng stator voltage frequency
STFive Applications
Voltage Frequency Relation
Fixing relation between voltage frequency F=F(V) possible eliminate control variable. voltage computed knowing frequency
Vmax
Vmin
Minimum Freq. Rated Freq (Stator Freq.)
STFive Applications
Constant Control Advantages
Simplest method control (linear relationship between Operates constant Flux Motor always supply maximum Torque Easy implementation
Drawbacks
Efficiencynot optimized Motor oversized
STFive Applications
Motor Efficiency Optimization through Flux adaption Torque request
Torque rated
rated curve
f=constant
WORKING ZONE
Flux =rated
T,rated
ADJUSTING STATOR VOLTAGE
0.8f 0.6f 0.4f 0.2f slip frequency
f-fr
1.0f
slip
slip=constant
STFive Applications
Slip Control: Fuzzy Algorithm
Stator Voltage Loop
Torque rated
rated curve
f=constant
T,rated
Flux =rated
1.0f
ADJUSTING STATOR VOLTAGE
0.8f 0.6f 0.4f 0.2f slip frequency f-fr slip
Adjusting Stator Voltage
Slip
Stator Frequency
STFive Applications
Slip Control: Fuzzy Algorithm
Stator Frequency Loop
Torque/T, rated
rated
rated
fsl1
fsl2
fsl3 fsl4
rotor speed increasing Stator Frequency increases
Adjusting Stator Frequency
Speed error
Error derivative
STFive Applications
Slip Control: Complete Loop Diagram
Speed Setpoint
Speed Error
Fuzzy algorithm
rotor speed Slip Setpoint
Error Derivative
Stator frequency increment
Slip Error
Fuzzy algorithm
Stator Voltage
Actual Slip
STFive Applications
Variable Frequency converter
order change stator voltage frequency necessary variable frequency converter. variable frequency converters, which interface between utility power system induction motor, must satisfy following basic requirements:
Ability adjust frequency according desired output speed Ability adjust output voltage maintain constant flux constant torque region. Ability supply rated current continuous basis frequency.
STFive Applications
Variable Frequency converter
variable frequency converter implemented using different techniques:
Pulse width modulated voltage source inverter (PWM VSI) Square wave voltage source inverter (square wave step modulation)
Variable Frequency Converter line
Rectifier
Filter
Inverter
Motor Output (variable voltage frequency)
STFive Applications
Square Wave Inverter: step modulation
inverter operates square wave mode which results phase motor neutral voltage With square wave inverter operation, each inverter switch total three switches instant time Because inverter operating square wave mode, magnitude motor voltage controlled controlling
Motor phase voltage
STFive Applications
Square Wave Inverter: step modulation
order implement step modulation inverter must driven using following signal:
THREE PHASE INVERTER
Link
Changing frequency three signals possible change frequency stator voltage.
STFive Applications
step modulation ST52x301
three square wave easily obtained using digital Timer ST52x301. square wave obtained writing sequentially selected digital port following number:
(binary) (decimal)
timer used change speed writing sequence numbers. this frequency square wave modified
STFive Applications
step modulation ST52x301
magnitude stator voltage modified using ST52x301. order change value stator voltage square wave connected gate with high frequency PWM. high frequency then switching frequency inverter transistors. using this method line line rms. voltage about V(rms) 0.78*Vd*d where duty cycle
STFive Applications
step modulation ST52x301
ST52T301
Timer
Digital
order avoid cross conduction problem "dead time" must added between
STFive Applications
Closed loop control ST52T301
ST52T301
Ref.
Timer Digital
Speed
this case ST52T301 duty cycle (stator voltage magnitude) Timer counter (stator voltage frequency) modified using fuzzy standard algorithm order minimize error between Ref. rotor speed. V/F=K control method fuzzy variation successfully applied large class applications.
STFive Applications
Sinewave Modulation
Stator speed varying reading patterns
=1/32*Voltage*sin(ptk =1/32*Voltage*sin(ptk -2/3o) =1/32*Voltage*sin(ptk +2/3o)
tk+1-tk=T*8ls F=1/[24*(tk+1-tk)]
voltage level
frequency
STFive Applications
Sinewave Modulation with ST52
Each instantaneous Voltage value generate addressing pointer values look-up-table where stored unitary sampled sinewave Voltage amplitude obtained using multiply division capability ST52x420 Stator Frequency obtained changing patterns scan speed using interrupt output given internal timers ST52x420
STFive Applications
Three-phase Motor Control Board with ST52x420
Available Contact further information st52.support@st.com
STFive Applications
example step modulation implementation ST52x301 FUZZYSTUDIO environment
Main program
STFive Applications
Peripherals Configuration
FUZZYSTUDIO3.0 TRIAC driver dialog
STFive Applications
TIMER driver dialog
Definition Fuzzy Control FUZZYSTUDIO
STFive Applications

Three-phase Motors Three-phase induction motors brushless motors.

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